Inert intermediate adhesive layer for a fluorescent substance in a fluorescent electronic tube

ABSTRACT

In a fluorescent electronic tube of the type wherein a layer of fluorescent substance is coated upon an anode electrode or an insulator and is excited to luminesce by electrons from a cathode electrode, there is provided an intermediate layer between the layer of fluorescent substance and the anode electrode or insulator. The intermediate layer is composed of a metallic conductor or a semiconductor material which is inert to the fluorescent substance and does not interfere with the flow of electrons.

United States Patent Tanji 1 Sept. 16, 1975 [54] INERT INTERMEDIATE ADHESIVE LAYER 3,560,784 2/1971 Steele et a1. 313/92 FOR A FLUORESCENT SUBSTANCE IN A 3567984 3/1971 Allard 3,571,655 3/1971 Tammoto 313/1095 X FLUORESCENT ELECTRONIC TUBE [75] Inventor: Mikiharu Tanji, lsc, Japan [73] Assignee: Ise Electronics Corporation, lse,

Japan [22] Filed: July 21, 1970 [2]] App]. No.: 56,818

[30] Foreign Application Priority Data July 22, 1969 Japan 44-69158[U] [521 U.S. Cl. 313/496; 156/67; 313/483; 313/510 [51] Int. Cl. I'IOIj 29/22 [58] Field of Search 313/1095, 92, 221, 109, 313/108 R; 252/506; 117/335 C; 156/67 [56] References Cited UNITED STATES PATENTS 3,525,679 8/1970 Wilcox et a1 313/92 R X FOREIGN PATENTS OR APPLICATIONS 405,964 2/1934 United Kingdom 313/92 R Primary Examiner--Palmer C. Demeo Attorney, Agent, or FirmCharles E. Pfund, Esq.

[5 7 ABSTRACT In a fluorescent electronic tube of the type wherein a layer of fluorescent substance is coated upon an anode electrode or an insulator and is excited to luminesce by electrons from a cathode electrode, there is provided an intermediate layer between the layer of fluorescent substance and the anode electrode or insulator. The intermediate layer is composed of a metallic conductor or a semiconductor material which is inert to the fluorescent substance and does not interfere with the flow of electrons 1 Claim, 3 Drawing Figures PATENTEI] SEP I 6 I975 2 PRIOR ART FIG.

PRIOR ART FIG.

FIG.

INVENTOR.

MIKIHARU TANJI INERT INTERMEDIATE ADHESIVE LAYER FOR A FLUORESCENT SUBSTANCE IN A FLUORESCENT ELECTRONIC TUBE BACKGROUND OF THE INVENTION This invention relates to a fluorescent electronic tube such as a fluorescent display tube or a synchronism indicating tube wherein a fluorescent layer coated on a metal anode electrode or an insulator is caused to luminesce by the excitation of electrons emanated from a cathode electrode disposed in opposed relationship with the anode electrode or insulator, and more particularly to the improvements of its electrode construction.

A prior fluorescent display tube is typically constructed as shown in FIGS. 1 and 2 of the accompanying drawing. More particularly, it comprises a glass envelope 1 similar to that utilized in a conventional electronic tube and a vertical insulating substrate 2 of ceramic or mica supported in the envelope by a pedestal 3 and horizontal mica plates 4. Discrete twelve letter display electrodes or anode electrodes 5 each coated with a layer 6 of fluorescent substance are mounted on the front surface of the insulating substrate to form desired letters or numerals when they are energized selectively. Any one of well known fluorescent materials such as ZnS Ag, (emanating blue colour), ZnS Cu (emanating green colour), Zn (PO Mn (emanating red colour) may be selected. Lead wires 7 for respective electrodes are inserted through the substrate from the rear surface thereof, opposite ends of lead wires being connected to respective terminal conductors 8 extending through the envelope 1. A cathode electrode 9 in the form of a filament of 30 to 50 microns diameter is mounted in front of the anode electrodes 5 by upper and lower supporting rods 10 and 11. Opposite terminals of the cathode electrodes are also connected to appropriate terminal conductors 8.

As above described, in this type of the prior art fluorescent display tube or fluorescent electronic tube the layers of fluorescent substance are coated directly on the anode electrodes 5.

l have found that the luminous efficiency of the fluorescent tube which is generally operated at a relatively low voltage is greatly reduced by contaminants and oxides on the metallic surface of the anode electrodes 5 which contaminate or interfere with the flow of electrons. Further I have found that even if such contaminants and oxides were removed from the metallic surface of the anode electrodes 5, the fluorescent substance is contaminated by the gas evolved from the anode electrodes 5 or metal during the operation of the electronic tube thus reducing the quantity of light emanated therefrom.

SUMMARY OF THE INVENTION It is therefore an object of this invention to eliminate causes that decrease the luminous efficiency of a fluorescent electronic tube having an electrode construction as above described.

According to this invention there is provided a fluorescent electronic tube of the type wherein a layer of fluorescent substance coated upon an anode electrode or an insulator is excited to luminesce by electrons from a cathode electrode disposed to oppose the anode electrode or insulator characterized by an intermediate layer interposed between the layer of fluorescent substance and the anode electrode or insulator, said intermediate layer being composed of a metallic conductor or a semiconductor material which is inert to the fluorescent substance and does not interfere with the flow of electrons.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 shows a longitudinal section of a prior art fluorescent display tube;

FIG. 2 shows a side view, partly in section of the tube shown in FIG. 1 and FIG. 3 is an enlarged perspective view of essential component parts of a fluorescent electronic tube constructed according to the teaching of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to FIG. 3 which shows an enlarged perspective view of essential component parts of a fluorescent electronic tube constructed according to this invention, a cathode electrode 22 comprises a filament 21, and a layer of fluorescent substance 23 is coated on an anode electrode of metal 25 through an intermediate layer 24. When a voltage is impressed across cathode electrode 22 and anode electrode 25 electrons 26 excite the layer of fluorescent substance 23 to emanate fluorescence 27.

It is advantageous to construct the intermediate layer 24 from electroconductor or semiconductor material so as not to interfere with the flow of electrons when energizing the fluorescent substance 23 to fluoresce. Further, the material should be stable or inert to the fluorescent substance.

Although there are many materials which can be used to form the intermediate layer they should not evolve gasses and not readily be oxidized. Metals, ordinary conductors or semiconductors are suitable for this purpose but a preferred material is considered to be a mixture of carbon powder and a small quantity of water glass because it is relatively stable and has relatively high conductivity.

My experiment showed that a fluorescent tube prepared by coating the mixture of carbon powder and water glass on the surface of anode electrodes 25 and then coating the layers of fluorescent substance 23 on the intermediate layer produced brightness twice as large as that of a tube having layers of fluorescent sub stance directly upon the surface of anode electrodes. This means increased luminous efficiency of the fluorescent substance.

While in the above described embodiment the fluorescent substance is applied on the surface of anode electrodes of metal, in the case where the fluorescent substance is applied on the surface of an insulator, the same problems are encountered due to contamination of the insulator. Accordingly it is clear that this invention is also applicable to such a tube with the same advantageous result.

Thus this invention can increase the brightness of fluorescent substance by simple means whereby to provide an efficient display tube or synchronism indicating tube capable of operating at a low operating voltage.

What is claimed is:

1. In a fluorescent electronic tube wherein a layer of fluorescent substance coated over a supporting member is excited to luminesce by electrons supplied from conduct electrons so as not to interfere with the flow of electrons when the fluorescent substance is energized to fluoresce, and which comprises a mixture of powdered carbon and water glass. 

1. IN A FLUORESCENT ELECTRONIC TUBE WHEREIN A LAYER OF FLUORESCENT SUBSTANCE COATED OVER A SUPPORTING MEMBER IS EXCITED TO LUMINESCE BY ELECTRONS SUPPLIED FROM A CATHODE ELECTRODE DISPOSED TO OPPOSE SAID SUPPORTING MEMBER, THE IMPROVEMENT WHICH COMPRISES AN INTERMEDIATE LAYER WHICH IS INTERPOSED BETWEEN SAID FLUORESCENT SUBSTANCE AND SAID SUPPORTING MEMBER, SAID INTERMEDIATE LAYER BEING COMPOSEDOF A MATERIAL WHICH IS INERT TO SAID FLUORESCENT SUBSTANCE, WHICH IS ADAPTED TO CONDUCT ELECTRONS SO AS NOT TO INTERFERE WITH THE FLOW OF ELECTRONS WHEN THE FLUORESCENT SUBSTANCE IS ENERGIZED TO FLUORESCE, AND WHICH COMPRISES A MIXTURE OF POWDERED CARBON AND WATER GLASS. 